Rotor, electric motor, air conditioner, and method for manufacturing rotor

Abstract

A rotor includes a yoke that is formed annularly and a resin magnet integrated with the yoke. The yoke includes a first inner circumferential surface, a second inner circumferential surface, and a third inner circumferential surface. The second inner circumferential surface is adjacent to the first inner circumferential surface, and has a radius larger than a radius of the first inner circumferential surface. The third inner circumferential surface is adjacent to the second inner circumferential surface, and has a radius larger than both of the radius of the first inner circumferential surface and the radius of the second inner circumferential surface.

1 . A rotor comprising:
 a yoke portion that is formed annularly; and   a magnet portion integrated with the yoke portion,   
       wherein
 the yoke portion includes 
 a first inner circumferential surface, 
 a second inner circumferential surface adjacent to the first inner circumferential surface and having a radius larger than a radius of the first inner circumferential surface, and 
 a third inner circumferential surface adjacent to the second inner circumferential surface and having a radius larger than both of the radius of the first inner circumferential surface and the radius of the second inner circumferential surface. 
 
     
     
         2 . The rotor according to  claim 1 , wherein the yoke portion includes a first step formed between the first inner circumferential surface and the second inner circumferential surface. 
     
     
         3 . The rotor according to  claim 2 , wherein the yoke portion includes a second step formed between the second inner circumferential surface and the third inner circumferential surface. 
     
     
         4 . The rotor according to  claim 1 , wherein a difference between the radius of the first inner circumferential surface and the radius of the second inner circumferential surface is 0.1 mm or more in a radial direction of the rotor. 
     
     
         5 . The rotor according to  claim 1 , wherein a difference between the radius of the second inner circumferential surface and the radius of the third inner circumferential surface is 0.1 mm or more in a radial direction of the rotor. 
     
     
         6 . The rotor according to  claim 1 , wherein the first inner circumferential surface is a surface extending in parallel with an axial direction of the rotor. 
     
     
         7 . The rotor according to  claim 1 , wherein the first inner circumferential surface is an inner circumferential surface formed on an end portion of the yoke portion in an axial direction of the rotor. 
     
     
         8 . The rotor according to  claim 1 , wherein the third inner circumferential surface is formed like a tapered shape so as to gradually widen in a direction opposite to the second inner circumferential surface. 
     
     
         9 . The rotor according to  claim 1 , wherein the yoke portion is a thermoplastic resin containing a soft magnetic material as a main component. 
     
     
         10 . The rotor according to  claim 1 , wherein the yoke portion is a thermoplastic resin containing a ferrite magnet as a main component. 
     
     
         11 . The rotor according to  claim 1 , wherein the magnet portion is integrated with the yoke portion outside the yoke portion in a radial direction of the rotor. 
     
     
         12 . The rotor according to  claim 1 , wherein the magnet portion is a thermoplastic resin containing a rare earth magnet as a main component. 
     
     
         13 . An electric motor comprising the rotor according to  claim 1 . 
     
     
         14 . An air conditioner comprising:
 an indoor unit; and   an outdoor unit connected to the indoor unit, wherein   at least one of the indoor unit and the outdoor unit includes the electric motor according to  claim 13 .   
     
     
         15 . A method for manufacturing a rotor including an annular yoke portion having a first inner circumferential surface, a second inner circumferential surface adjacent to the first inner circumferential surface, and a third inner circumferential surface adjacent to the second inner circumferential surface, the method comprising the steps of:
 forming the first inner circumferential surface, the second inner circumferential surface having a radius larger than a radius of the first inner circumferential surface, and the third inner circumferential surface having a radius larger than both of the radius of the first inner circumferential surface and the radius of the second inner circumferential surface, by injecting a thermoplastic resin into a mold including a runner into which the thermoplastic resin is injected and a molding portion to mold the thermoplastic resin into the yoke portion; and   separating a first part formed in the runner from a second part formed in the molding portion.